There's not really one right answer - and as Apple showed with the click wheel, a product designer can come up with a completely new way of interacting with a device and it'll completely change the landscape. Sadly so far it looks like a lot of readers have been designed by industrial designers and are more technical exercises, rather than product designers with an eye on user interaction. There are very, very few people and companies that have that particular skill set.

It's not just a question of moving the buttons around, but let's be honest you can see ebooks are still in their infancy when even that detail is weak in current devices.